Haptics is a tactile and force feedback technology that takes advantage of a user's sense of touch by applying haptic feedback effects (i.e., “haptic effects”), such as forces, vibrations, and motions, to the user. Devices, such as mobile devices, touchscreen devices, and personal computers, can be configured to generate haptic effects. In general, calls to embedded hardware capable of generating haptic effects (such as actuators) can be programmed within an operating system (“OS”) of the device. These calls specify which haptic effect to play. For example, when a user interacts with the device using, for example, a button, touchscreen, lever, joystick, wheel, or some other control, the OS of the device can send a play command through control circuitry to the embedded hardware. The embedded hardware then produces the appropriate haptic effect that is perceived by the user.
Devices that generate haptic effects typically rely on batteries as their source of power. Battery life has always been an issue, however as devices become more sophisticated, power consumption becomes even more of a design issue. Therefore, methods to reduce power consumption are a critical portion of product design.
Many different haptically-enabled devices exist that include a haptic system for the generation of haptic effects. For many of these devices, especially non-mobile devices, the power consumption needed to generate haptic effects is largely irrelevant. However, power consumption, and battery life, is always a key concern in mobile devices. Longer life between charges is seen as very valuable by consumers. Even with mobile devices such as smartphones, where minimizing the power consumption associated with mobile device applications is a constant concern, the power consumption from haptic effects in relatively small. Studies have shown that under worst-case usage scenarios for a 24-hour period, typical haptic effects consume from 0.95 to 4.11 percent of the device battery capacity, depending on the use case.
However, wearable devices generally have an increased need to reduce power consumption. Most wearable devices are expected to last many days or weeks between charges, as opposed to some smartphones that are expected to be charged nightly. As a consequence, wearable devices have a tight energy budget for generating haptic effects in view of a typically (e.g., ˜250 mAh) battery that is expected to work for up to 7 days between charges. Relative to smartphones, the haptic effects on a wearable device can potentially consume a large percentage of the power budget.